[Kernel] Remove redundant Exp calculations

[DefTruth]

Remove redundant Exp calculations

[github-actions]

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[DefTruth]

@LucasWilkinson PTAL, thanks~

[LucasWilkinson]

LGTM, thanks for the contribution!

[DefTruth]

@LucasWilkinson some tests failed, but it seems not related to this PR.

[DefTruth]

weird, i don't why the mamba kernel tests failed

FAILED kernels/test_mamba_ssm_ssd.py::test_mamba_chunk_scan_cont_batch[seq_len_chunk_size_cases0-5-8-itype0]
 AssertionError: chunk_indices and chunk_offsets should have been set

[DefTruth]

The mamba ssd kernel test failed, related PR #16623